Electrodeposition of metals



Patented in, 21, 1942 ELECTRODEPOSITION 0F METALS Rudolf Lind, Euclid, William J. Harshaw, Shaker Heights, and Kenneth E. Long, South Euclid, Ohio, assignors to The Harshaw Chemical Company, Elyria, Ohio, a corporation of Ohio No Drawing. Application February 9, 1940, Serial No. 318,138

10 Claims.

This invention relates as indicated to electrodeposition of metals and more specifically, to. a process of and materials for use in the process of electrodepositing nickel characterized in that the resultant nickel plate, as deposited is both bright and ductile. More particularly, the present invention has to do with new addition agents for producing the above-named desirable characteristics in the nickel plate and which may be used with acid nickel baths of usual composition perating under usual conditions.

In order to properly evaluate the present invention, it is necessary to define brightness and ductility or brittleness, terms used in the old art, but used loosely to describe all degrees of brightness or brittleness.

Brightness a chromium. If a heavier deposit is plated out,

the brightness of the highly buffed surface diminishes and a gray or white dull deposit is obtained.

A nickel plate which is thick enough to be practical for use and which is bright without bufiing is not only desirable per se, but it is particularly advantageous where it is destined for use as the base for an electrolytically deposited chromium plate,'since, if the nickel platedoes not require to be polished and buffed, a relatively thin plate gives the same protection as the necessarily heavier gray plate. some of which must be taken off in the polishing to secure the desired brightness. Furthermore, a very considerable saving in time and in cost on the production of plated articles becomes possible, whether with nicked plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to time for inclusion in nickel plating baths in order to control or affect the character of the electrolytically deposited metal. One principal objective in such modification of the plating bath has been to increase the,brightness or luster of the deposited metal.

Many of these previous nickel plating addition agents have allowed a much heavier deposit of nickel to be built up before thebrightness of the base metal was materially diminished. When polished articles are plated in suchbaths, the deposit is not truly bright but merely; at best, has

the same character as the base metal. The brightness produced by such addition agents may, therefore, be characterized as brightness diminishing with increased thickness of plate on a polished surface."

Others of these previous nickel plating addition agents have produced a plate which would maintain the brightness of the polished base surface, even though the plate was built up to a substantial thickness. They would not build up any substantial brightness on an unpolished surface and, at best, would only very slowly build up brightness on an unpolished surface when plates of extreme thickness were made. The brightness produced by such addition agents may, therefore, be characterized as brightness maintaining itself with increased thickness of plate on a polished surface. 1 l

The addition agents of the present invention produce a plate that not only maintains the brightness of the most highly polished base metal, irrespective of the thickness of the plate within practical limits, but also increases in brightness with increase in thickness of theplate on an unpolished surface. The brightness produced by such addition agents may, therefore, be characterized as brightness increasing with thickness of plate on an unpolished surface.

Ductility .The question of ductility is one of vital concern to the plater. In general, all bright plates are harder and, therefore, more brittle than ordinary dull nickel. When enough of many of the previously employed addition agents was added to a bath to produce a bright plate, the plate was often too brittle for commercial use and yet if less' additionagent was used,'the plate would not be fully bright.

A test for ductility may be made by plating on a non-adherent surface and stripping ofi thefoil and bending it double, on itself. A plate .001" thick which will pass this test without breaking is considered to have good ductility. A plate .0005" thick which will just pass this test is considered .to have passable ductility. 'A plate .0002" thick which Will not pass this test'without breaking is considered to have poor ductility. The addition agents of the present invention not only produce plates with the highest order of brightness, but also with a high order of ductility as defined by the above scale. This'is desirable and essential to the practical use of bright nickel plating.

The principal object of the present invention,

' therefore, broadly stated, is to provide an improved process of and materials for use in the process of electrodepositing nickel which will not only render the nickel plate desirably bright but which will also preserve or render the plate de- C9 sirably ductile.

the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter more particularly pointed out tively selected from certain different classes of compounds, we are able to produce deposits which are superior to those obtainable by the use of addition'agents from either one of such classes alone. We find that the addition agents from one of said classes, although characterized by an embrittling tendency, are productive of extreme brightness when used in combination with addition agents from the other class and that addition agents from said other class not only cooperate in the production of brightness but also exert a ductilizing effect in the combination. The use of one addition agent from each class is preferable but a plurality from each class can be used successfully. Our cooperating addition agents are suitable for use in a wide variety of nickel electroplating solutions. We have found them to be very effective in aqueous acid nickel sulfate solutions and aqueous acid nickel chloride solutions. Among the nickel sulfate solutions in which they are effective are aqueous acid solutions of nickel sulfate, nickel sulfate and nickel chloride, nickel sulfate and sodium chloride, nickel sulfate and hydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfate and alkali metal chlorides other than sodium chloride, the chlorides serving to produce good Chrysoidine p-Amino azo benzene (Aniline Yellow) 'lriamino azobenzene Brilliant Croceine 33A Pontamine Yellow SX Pontachrome Blue R Direct Blue D 313 anode corrosion. Our addition agents are effective -in nickel chloride solutions with and without nickel sulfate. In each of said solutions it is desirable, although not necessary, to employ boric acid or another suitable buffering agent. We prefer to employ a bath containing nickel sulfatetogether with a suitable chloride, preferably nickel chloride and a suitable buffer, preferably boric acid. We prefer to employ one or more addition agents from one of said classes in quantity to produce the desired brightness and one or more from the outer class in quantity to overcome to a substantial extent the resulting embrittling tendency.

Representative of separate classes of compounds which, when used in combination as above stated, produce improved results, are (1) azo compounds containing the group Ar N:N Ar which are soluble in the plating bath to the extent of at least one milligram per liter, and (2) aromatic sulfonates, sulfonamides and sulfimides soluble in the bath to the extent of at least A; gram per'liter. Since these two classes of addi- 2,290,342 Other objects-of our invention will appear as.

tion agents are distinct, they will be discussed separately. nzo Courouups Our invention contemplates, as indicated, the use of azo compounds containing the group Ar N:N Ar. Ar and Ar may be be identical or different. The group Ar N:N Ar may be repeated as in the bis-azo compounds and tris-azo compounds. Likewise, compounds of the form Ar N:N Ar N:N Ar" are within the scope of our invention. Ar, Ar, etc., indicate aromatic, cyclic structures such as, for example, benzene or naphthalene nuclei which may and preferably, although not necessarily, do carry substituents. .We prefer to employ compounds carrying one or more amino groups connected to ring carbon. Alkyl amino substituents such as N(Me)z, NHMe and the like (not more than 3 carbon atoms) also are desirable and may be regarded as amino groups. Compounds containing alkyl, such as methyl, ethyl, etc., halogen, sulfonate, hydroxy and ultra groups may also be used. The substituent groups such as amino groups, including allryl amino groups, appear to be desirable as such, while groups such as the sulfonate and halogen groups, unless needed to improve the solubility, apparently are undesirable or indifferent.

The salts of such of these compounds as are basic, e. g. the chlorides, hydrochlorides, acetates and sulfates are to bepreferred to such basic compounds themselves because of their greater solubility. It is essential that these compounds, a single one or a mixture of two or more thereof, be present in the solution to an extent to exert their brightening effect, preferably at least 2 milligrams per liter.

Some specific examples of compounds suitable for our purpose are as follows, being identified where possible by reference to Farbstofltabellen by Gustav Schultz, 7th edition, volume I, 1931.

Table I Schultz No. 27 Schultz N0. 26

Schultz No. 639 CH Schultz No. 704

Schultz No. 208 Schultz No. 471

While the quantity of these substances employed is not sharply critical, they are used in small amounts, that is, amounts on the order of 2 to 100 milligrams per liter of the bath, the upper. limit being determined by their embrittling effect and in some cases, the solubility in the bath. These compounds are capable of producing, in the absence of compounds of the second class, deposits which are brightbut brittle, and are used in quantities less than required to produce maximum brightness in the absence-of any compound of the second class.

Most of the specific examples given in Table I are commercial products. There are many other members of the same groups, mostly not commercial products or not obtainable in pure form,

' (Ph N:N Ph) carrying at least one amino group on one or both benzene rings but not more than three amino groups on either benzene ring and their salts such as chloride, hydrochloride, acetate and sulfate are of outstanding value from the standpoint of control of the operation of the bath and are somewhat superior in respect to brightening effect to the more complex compounds.

The second class of materials, representative particular ones of which are employed in combination with one or more substances of the first class of compounds above identified, may be and for the purposes of this specification are designated as aromatic sulion-compounds. These materials are capable of cooperating with the materials of the first class to produce nickel deposits having a high order of brightness accompanied by commercial ductility. Particular ex? amples which we have found to give excellent results are as follows:

Table II Alpha-naphthalene mono-sulfonate Beta-naphthalene mono-sulfonate Naphthalene disulfonates Naphthalene trisulfonates Sulfonated naphthalent o- Benzoic sulfimide (saccharin,

preferably as sodium salt) 1" Benzene sulfonamide Benzene sulfohydroxamic acid p- Toluene sulfonamide 10. o- Toluene sulfonamide The above named addition agents of this second class, suitably in the form of the sodium or the nickel salt, may be used in various quantities upwards from 0.2 g./l., however, 5 g./l.-or less is usually sufficient concentration for best results. Larger quantities, within the limits of solubility, do no harm.

Specific Example 5 of Table II above is such as may be produced by reacting 2 parts of oleum on one part of naphthalene at 160 C. for two hours, neutralizing the resulting mixture with nickel carbonate, filtering and diluting to ""B. Where quantities of sulfonated naphthalene are referred to hereinafter, it is to be understood that the quantity specified represents roughly the nickel-naphthalene-mixed-sulfonate content of the mixture. Five cc. of the nickel neutralized reaction mixture is taken as equivalent to one gram of nickel-naphthalene-mixed sulfonates. Other mixtures of compounds of the second class of materials also are satisfactory.

A conventional aqueous acid nickel bath in which the combined use of the two classes of addition agents will be found to give improved results, as above indicated, consists of Where this compound is referred to, the material sold is to be under the tradename of Duponol M. E Dry understood. It is sold as the technical compound. Other equivalent surface tension reducing agents may be used instead of Duponol. Preparations known as Tergitol 7 and Tergitol 08, sold by Carbide 8: Carbon Chemicals Co. and said to be sodium secondary alcohol sulfates, may be used instead of Duponol. The quantities required are of the same order.

"Some heptahydrate is usually present. Where nickel sulfate is used herein in specific examples, this mixture of hydrates is to be understood.

In the above table giving the composition of a conventional bath; sodium lauryl sulfate is added for the purpose of reducing the surface tension in order to prevent pitting of the plate. The sulfates of normal primary aliphatic alcohols, having from 8 to 18 carbon atoms, are a class of compounds preferred for use for this purpose.

Following are a number of specific examples of bath compositions, each liter of which con tains the substances indicated.

Example I NlSO4.6H2O 240 grams NiCl2.6H2O 37.5 grams HaBOs 37.5 grams Sodium lauryl sulfate (Tech) 0.25 gram "Sulfonated naphtha1ene 20 cc. Chrysoidine -1- 10 milligrams H2O to make 1 liter 7 pH 3.0 Temperature"; 50 C. Current density 40 amp/sq. ft.

Example II NiSO4.6HzO 240 grams NiCh.6HzO 37.5 grams H330: 37.5 grams Sodium lauryl sulfate (Tech.) 0.25 gram "Sulfonated naphthalene 20 cc. Saccharin (soluble soda salt) 0.5 gram Tri amino azobenzene 15 milligrams rho to make 1 liter 9 I 3.5 Temperature 55 C. Current density 60 amp./ sq. ft.

Example III NiSO4.6H2O 240 grams NiCl2.6H2O 37.5 grams H3303 37.5 grams Sodium lauryl sulfate (Tech) 0.25 gram Sulfonated naphthalene 20 cc. Pontachrome Blue R 10 milligrams H20 to make. 1 liter pH 3.5 Temperature 45 C. Current density 50 amp./ sq. ft.

This application is a continuation-in-part of our co-pending application Serial No. 217,774, -filed July 6, 1938, now Patent No. 2,238,861.

This application is also a continuation-in-part of our co-pending applications Serial Nos. 309,- 232 and 309,233, filed December 14, 1939, now Patents No. 2,198,267 and No. 2,198,268, respectively and which were in turn continuations-inpart respectively of applications .Serial Nos. 200,120 and 200,121, filed April 5, 1938.

Having thus. described our invention, what we claim is:

1. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an azo compound containing the group Ar N:N Ar and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, single ring aryl sulfonamides and single ring aryl sulfimldes and mixtures thereof, the azo class of addition agents being present in amounts of from 1 to milligrams per liter of the bath to exert their brightening eifect, whereas the second class of addition agents is present in amounts upward from 0.2 gram per liter, the last group of addition agents having no azo group.

2. An electroplating bath comprising an aqueous acid solution of a nickel electrolyte of the class consisting of nickel sulfate andnickel chloride, said solution having the capability of producing bright and ductiledeposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an azo compound containing the group Ar N:N Ar, such being present in amounts of from 1 to 100 milligrams per liter of the bath and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof, this second class of addition agents being present in solution in the bath 'to the extent of at least gram per liter, the last group of addition agents having no azo group.

3. An electrodeposition bath as defined in claim 1 wherein the first mentioned addition agent is chrysoidine.

4. An electrodeposition bath as defined in claim 1 wherein the first mentioned addition agent is an amino substituted azo benzene having from one to three amino groups carried by ring carbon.

5. An electrodeposition bath as defined in claim 1' wherein said first mentioned addition agent is an amino substituted azo benzene having from one to three amino groups carried by ring carbon and said second mentioned addition agent is saccharine.

'6. An electroplating bath containing nickel sulfate and a compound of the class consisting of nickel chloride, ammonium chloride, hydrochloric acid and alkali metal chloride, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an azo compound containing the group Ar N:N Ar, such being present in amounts of from 1 to 100 milligrams per liter of the bath and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof soluble in the bath to the extent of at least /2 gram per liter, the second type addition agent having no azo groups.

'7. An electroplating bath containing nickel sulfate, boric acid and a compound of the class consisting of nickel chloride, ammonium chloride, hydrochloric acid and alkali metal chlorides, said bath having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an azo compound containing the group Ar N:N Ar said azo class of addition agents being present in amounts of from 1 to 100 milligrams per liter of the bath and the other of said addition agents being selected from the group consisting of naphthalene sulfonates, single ring aryl sulfonamides and single ring aryl sulfimides and mixtures thereof, this second class of addition agents being present in solution in the bath to the extent of at least gram per liter, the second type addition agent having no azo groups.

8. An electrodeposition bath comprising an aqueous, acid bath containing one or more substances of the class consisting of nickel sulfate,

nickel chloride and mixtures thereof said bath also containing cooperating addition agents having-jointly the capability of producing bright and ductile deposits of nickel, the first class of addi tion agent being azo type compounds containing the group Ar N:N Ar and having at least one amino group connected to ring carbon, and the second class of addition agents being selected from the group consisting of naphthalene sulfonates, single ring aryl sulfonamides and single ring aryl sulfimides wherein said first named addition agent is maintained in solution in the bath in quantity from 2 to milligrams per liter and the second named addition agent is maintained in solution in the bath in quantity from gram per liter to saturation, the second type addition agent having no azo groups.

9. An electroplating bath comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, wherein one of said addition agents is an amino substituted azo benzene havingfrom one to three amino groups carried by ring carbon and the second addition agent is a naphthalene sulfonate, said amino substituted azo benzene being maintained in solution in the bath in quantity from 2 to 100 milligrams per liter and said naphthalene sulfonate being maintained in solution in bath in quantity at least /2 gram per liter.

10. An electroplating bath comprising anaqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, wherein one of the said addition agents is an amino substituted azo benzene having from one to three amino groups carried by ring carbon and the second addition agent is saccharine, said amino substituted azo benzene being maintained in solution in the bath in quantity from 2 to 100 milligrams per liter and saccharine being maintained in. solution in the bath in quantity at least gram per liter.

RUDOLF LIND. WILLIAM J. HARSHAW. KENNETH E. LONG. 

